肾功能轻度减低的内生肌酐清除率为
A.90~71ml/分B.70~51ml/分C.50~31ml/分D.30~21ml/分E.20~11ml/分
参考答案:B
The five-year-old boy can ________ speak English ______ sing beautiful English songs. It's
incredible. [ ]
A. not; but
B. either; or
C. not only; but also
D. neither; nor
如图所示,大伟同学用一个距离手3m高的定滑轮拉住重100N的物体,从滑轮正下方沿水平方向移动4m,若不计绳重和摩擦,他至少做功______J.